Valve gear for axial or for radial engines



Nov.v 19, 1935. w. A. cooMBs VALVE GEAR FOR AXIAL OR FOR RADIAL ENGINES 2 snets-sheet 1 Filed Nov. 12, 1954 W. A. COOM BS VALVE GEAR FOR AXIAL OR FOR RADIAL ENGINES Nov. 19, 1935.

Filed Nov. l2, 1934 2 Sheets-Sheet 2 `Wl'lh'qm AuguswLus Coombsl Patented Nov. 19, 1935 i UNITED STATES PATENT GFFIQE VALVE GEAR FOR AXIAL OR FOR RADIAL ENGINES William Augustus Coombs, Prospect, South Australia, Australia Application November 12, 1934, Serial No. 752,680 In Australia March 15, 1934 3 Claims.

'5 an improved gear for driving the cam of such engines and also an improved arrangement of the Valves or push rods.

According to my invention the cam is driven by an epicyclic gear comprising a fixed toothed ring co-axial with the crank shaft and a planet wheel carried upon an eccentric on the crank shaft, the planet wheel engaging the ring and being co-nnected to the cam by links. The links are longer than the radius of the eccentric and engage in slots on the kcam so that they move Vthe cam by a succession of impulses. The cam is arranged to operate both the intake and exhaust valves of each cylinder from lobes in the same plane.

In order that my invention may be the more clearly understood however, will now describe it with reference to the accompanying drawings in which I .have shown my invention applied to the head of a seven cylinder engine of the type having its cylinders arranged parallel or radial about the axis of the crank shaft in which the valves themselves are arranged radially and in which arrangement no push rods are used, the valve stems engaging tappets.

In these drawings Figure 1 is a sectional end elevation of the cylinder head showing four valves only.

Figure 2 is an enlarged view of the cam and tappets.

Figure 3 is a side view of Fig. 2.

Figure 4 is an end elevation of the gear which drives the cam.

Figure 5 is a central sectional view of Fig. 2 on line 5-5 thereof but omitting the tappets.

Figure 6 is a central section of the cam and one of the valve stems. Y

Figure 7 is an enlarged diagram showing the paths followed by the two ends of the links which interconnect the cani and the planet wheel and indicating the distance of travel for equal units of time of those ends of the links which engage the cam.

The exhaust valves l and the intake valves 2 are of the usual mushroom type and are arranged alternately ina single plane at right angles to the axis of the crank shaft i and are positioned to have their stems radial about the axis of the crank shaft and to have their heads outward. The valves operate upon seatings in ports 5 in the cylinder heads and such ports are of usual or approved construction. The stems are slidable in guides t and each valve head is normally heid down on to its seating by a spring 'l encircling its guide and stein and confined between the guide and a washer 8 upon the inner end of the 5 For valve adjustment the inner end of each of the stems is provided with a cap 9 adjustable lengthwise upon the stern, preferably by screw threads, and adapted to be locked in place, prefn erably by a pin i@ passing through the cap S 10` and the stern and held in place by the washer 8 which has down-turned edges, the washer fitting over the cap 9 and being held in place by having the beiorementioned spring 'l bearing thereon.

The caps $3 upon the inner ends of the stems 15 of the valves 2 and 3 are engaged by tappets i2 (one to each) which in turn engage a cam irl upon which are operating lobes i5.

Each tappet i2 is pivoted at the one end to a pin iii upon the cylinder head or crank case and 20 has one side of its free end in engagement with the cap 9 upon the valve stem and has the other side of its free end in engagement with the c le. rThe latter side has an appropriately il bearing face l? or it may have a roller. The 25 pins it upon which the tappets E2 are pivoted are arranged in a circle concentric with the crank shaft t, and the pivoted ends of the tappets i2 are shaped to allow the free end of the next tappet to operate through it. 30'

The cam lli is rotatably mounted upon the crank shaft l and is co-axial therewith. It is in the same plane as the Valves i and 2 and is connected by links 2S to a planet wheel mounted upon an eccentric 2t secured to the 35 crank shaft. The links ZEE each have at their ends pins 2| and 22, the pins 2l engaging in forations 23 in the planet wheel 2b and the pins 22 engaging in slots 2e in the cam it.

The planet wheel 25 is free to rotate upon the 40 crank shaft i but it engages in an internally toothed ring 28 secured to the cylinder heads or to the crank case. This internally toothed ring is co-axial with the crank shaft li.

The speed of rotation of the cam il reiative to 45 the crank shaft l is governed by the ratio of diameter of the planet wheel E5 to that of the ring 28 and depends upon the number of cylinders in the engine. Likewise the number of lobes it upon the cam depends upon the number of cyl- 50 inders. Thus in an engine having seven cylinders as shown in the drawings, the speed of rotation of the cam must be one-sixth that of the crank shaft and the cam must have three lobes.

Referring to the lobes I5 of the cam I4 as 55 X, Y, and Z, and tc the cylinders as A, B, C, D, E, F and G consecutively (not according to their iiring order) each lobe I5 of the cam I4 operates the exhaust valve I and intake valve 2 of each cylinder in the following manner: Lobe X engages and lifts the exhaust valve of cylinder A for approximately half a revolution of the crank shaft. It then releases the exhaust valve, which is returned by its spring, and engages and lifts the intake valve of cylinder A for approxi- Y mately the next half revolution of the crank shaft. It then releases the intake valve and it is returned by its spring.

During the above complete revolution of the crank shaft the cam has rotated through onesixth revolution and for the next revolution of the crank shaft the valves of cylinder A are not operated as the lobes are spaced at one-third revolution of the cam.

rfWo-sevenths cf a revolution after the above cycle of cylinder A had commenced, lobe Y commenced to operate the exhaust valve of cylinder C and the saine cycle was carried out in this cylinder as Was carried out in A excepting that the entire cycle Was tWo-sevenths of a revolution of the crank shaft later.

When the crank had rotated through foursevenths of a revolution lobe Z commenced to operate cylinder E and for each further tvvosevenths oi a revolution of the crank shaft a f rtlier cylinder commences the cycle, thus lobe A next operates cylinder G, lobe Y operates cylinder B, lobe Z operates cylinder D and lobe X operates cylinder F, after which lobe Y operates cylinder A and so on.

The revolution oi the cam i5 is effected in impulses which are of such length and at such a period that the respective valves are rapidly lifted during an impulse, are held in their open position during the eriod between impulses and are dropped during the next impulse. This movement ensures quick opening and closing of the valves. In a seven cylinder engine as shown in the drawings there are twenty-one impulses during a complete revolution of the cam I4 and if Fig. 7 of the drawings is considered it Will be obvious how the impulses are eifected. In this ligure the line K indicates the path of travel of the pins 2i which connect the one end of each link 2t to the planet Wheel 25 While the line L indicates the path of travel of the pins 22 which connect the other end of each link 2) to the cam iii. It must be remembered that the pins 22 engage in the slots Eli as the distance between them constantly varies. The distances between the lines M indicate the rate of travel per unit of time of the pins 22 and show hoW they successively accelerate and then slovv down.

Describing how the impulses are effected particularly with reference to Fig. 7 and Fig. 2 rin which the links are inccated in similarpositions) it will be seen that, as the crank shaft Il turns through one revolution, the eccentric B is carried around with it and the planet wheel 25, owing to it engaging in the toothed ring Z8, is driven around in a direction cf rotation opposite to that of the crank shaft and at a slower speed, it turning only through one-seventhv revolution for one revolution of the shaft. The planet Wheel, at the same time as it moves through the one-seventh revolution, moves eccentrically about the crank shaft, causing the pins 2| of the links 2E] to move along a path as indicated by the curved lines K in Fig. 7, one revolution of the crank shaft 4 producing a length of movement of each pin 2I equal to the length of one curved line K. The pin 22 of each link moves concentrically about the crank shaft and as the pin 2I constantly changes its direction of travel relatively to the line L so the pin 2l (as the pin 22 moves along one path K) is at rst stationary and then commences to move, and as it moves along the path K towards its centre it accelerates, slowing down or coming to rest, or as shown in Fig. '7 it moves slightly counter-directional, as it reaches the other end of the path K. As there are three links 2li equally spaced and there are seven curved paths K the maximum speeds of the three pins 22 occur at diiferent (equally spaced) intervals and by making the slots 2.4i in the cam Id of appropriate length the cam is rotated by impulses, an impulse occurring Wherever the fastest moving pin 22 strikes the end of its slot 24.

The various parts are suitably lubricated and the planet Wheel, cam and tappets preferably run in oil.

What I claim is: l

1. A gearing arrangement to rotate the cam oi' engines having the cylinders arranged parallel or radial about the axis of the crank shaft, means comprising a ilxed toothed ring coaxial with the crank shaft of the engine, a planet Wheel in engagement with the ring, an eccentric secured upon the crank shaft carrying the planet wheel, and links each having at one end a pin engaging in a perforation in the planet Wheel and each having at its other end a pin engaging in a slot in the cam, the links Which connect the rotatable cam to the planet Wheel being longer than the radius of the eccentric.

2. A gearing arrangement to rotate the cam of engines having the cylinders arranged parallel or radial about the axis of the crank shaft and having exhaust valves and intake valves, means comprising a fixed tooth ring coaxial with the crank shaft of the engine, a planet wheel in engagement With the ring, an eccentric secured upon the crank shaft carrying the planet Wheel, and links each having at one end a pin engaging in a perforation in the planet wheel and each having at its other end a pin engaging in a slot in the cam, the effective length of the links being greater than the radius of the eccentric, and lobes upon the cam each operating in proper sequence both the intake and the exhaust valves of each cylinder.

3. Engines having the cylinders arranged parallel about the axis of the crank shaft, an improved valve gear comprising a xed tooth ring coaxial with the crank shaft of the engine, a planet Wheel in engagement with the ring, an eccentric secured upon the crank shaft carrying the planet Wheel, links each having at one end a pin engaginfT in a perforation in the planet Wheel and each having at its other end a pin engaging in a slot in the cam, the effective length of the links being greater than the radius of the eccentric, lobes upon the cam, and an exhaust valve and an intake valve for each cylinder, the valves being radially positioned and in one plane at right angles to the axis of the crank shaft, each valve being adapted to be operated in proper sequence by each lobe of the cam.

WILLIAM AUGUSTUS COOMBS. 

